Dental materials based on acrylic-ester phosphonic acids

ABSTRACT

Acrylic ester phosphonic acids of general formula (I), stereoisomers thereof and mixtures of these,  
                 
 
     wherein n is 1 or 2, on the condition that for n=1 R 1  has the meaning  
                 
 
     and for n=2 R 1  has the meaning  
                 
 
     R 2  is a C 1  to C 12  alkylene radical, C 4 -C 8  cycloalkylene radical or C 7  to C 15  alkylene phenylene radical; R 3  is hydrogen, a C 1  to C 5  alkyl radical or a C 1  to C 5  O-alkyl radical; and R 4 , R 5 , independently of each other, each stand for a C 1  to C 5  alkyl radical or a C 1  to C 5  O-alkyl radical.

[0001] The present invention relates to acrylic-ester phosphonic acidswhich have a high hydrolysis stability and are suitable in particularfor the preparation of dental materials.

[0002] Phosphonic acids capable of polymerization are of significance topolymer chemistry above all as comonomers and permit the preparation oforganic polymers with high thermal stability, good adhesive properties,low flammability and good solubility in polar solvents. For thispurpose, numerous monomeric phosphonic acids are synthesized andpolymerized with vinyl, dienyl, allyl or styryl groups capable ofpolymerization. An overview of phosphonic acids is provided byHouben-Weyl, Methoden der Organischen Chemie [Methods of organicChemistry], Volume E 20 (2^(nd) part), G. Thieme Verlag, Stuttgart-NewYork 1987, 1300 ff. Examples of such conventional polymerizablephosphonic acids are vinyl phosphonic acid, allylbenzene phosphonicacid, α-aminoallyl phosphonic acid, 1,3-butadiene or isoprene phosphonicacid, 4-vinylbenzene phosphonic acid or 2-(4-vinylphenyl)-ethanephosphonic acid. Phosphonic acids, in which the C═C grouping is bound tothe phosphorus atom directly or via an oxygen atom, such as e.g. invinyl phosphonic acid or ethyl phosphonic acid monovinyl ester, haveonly a low tendency towards homopolymerization, with the result thatonly homopolymers with a low molar mass can be obtained.

[0003] Dental materials based on polymerizable (meth)acrylic acidderivatives of phosphonic acids, such as e.g. 2-methacryloyloxyethylphosphonic acid, in which the (meth)acryl group capable ofpolymerization is bound to the phosphorus via an alkylene radical, areknown from DE 199 18 974 A1. These compounds can be polymerized easily,but are not hydrolysis-stable.

[0004] DE 197 46 708 A1 discloses polymerizable acrylic phosphonic acidswhich are hydrolysis-stable in aqueous solution, have good adhesiveproperties, can be polymerized with conventional radical initiators andare therefore suitable in particular as a component of dental materials.The acrylic phosphonic acids display in the form of their carboxylicacid esters a good solubility in water and polar organic solvents while,although in the form of carboxylic acids they are easily soluble inwater, they are barely soluble in organic solvents. The differentsolution behaviour of ester and acid can be disadvantageous in hydrousmaterials. The hydrolysis of the carboxylic acid ester to form freecarboxylic acid accompanied by the splitting-off of alcohol cansignificantly change the solubility of the monomers and can thus lead tothe partial or complete precipitation of the phosphonic-acid componentsand therefore influence the properties of the material.

[0005] DE 100 18 968 discloses dental materials based onhydrolysis-stable acrylamide and acrylonitrile phosphonic acids.

[0006] A. M. Kawamoto, M. M. Campbell, J. Chem. Soc., Perkin Trans. 1,1997, 1249 describe difluorovinyl phosphonate analogues ofphosphoenolpyruvate, which are intended to represent potentialinhibitors of the shikimic acid pathway.

[0007] Finally, phosphonic-acid derivatives, in which polymerizablegroups are bound via an amide group to a phosphonic acid group, such asfor example in 4-methacrylamido-4-methylpentyl-phosphonic acid, areknown from EP 1 169 996 A1. These compounds have only a low radicalpolymerization ability.

[0008] The object of the invention is to prepare acrylic phosphonicacids capable of polymerization which are characterized by a furtherimproved resistance to hydrolysis in comparison with known acrylicphosphonic acids.

[0009] According to the invention, this object is achieved by acrylicester phosphonic acids of general formula (I), stereoisomers thereof andmixtures of these,

[0010] in which

[0011] n is 1 or 2,

[0012] on the condition that

[0013] for n=1 R¹ has the meaning

[0014] and for n=2 R¹ has the meaning

[0015] R² is a C₁ to C₁₂ alkylene radical, C₄-C₈ cycloalkylene radicalor C₇ to C₁₅ alkylene phenylene radical;

[0016] R³ is hydrogen, a C₁ to C₅ alkyl radical or a C₁ to C₅ O-alkylradical; and

[0017] R⁴, R⁵ independently of each other, each stand for a C₁ to C₅alkyl radical or a C₁ to C₅ O-alkyl radical.

[0018] The individual alkyl and alkylene radicals can bestraight-chained, branched or cyclic.

[0019] The individual radicals R2, R3, R4 and/or R5 can be unsubstitutedor substituted by one or more substituents, such as Cl, Br, CH₃O, OH,COOH, CN, ═O, ═S, ═NR⁶ or —NR⁷—CO—C(═CH₂)CH₂—Y—R⁸—PO(OH)₂, preferablyCl, CH₃O, OH, COOH, ═O or ═NR⁶, wherein R⁶ and R⁷ independently of eachother, each stand for hydrogen, a straight-chained or branched C₁ to C₁₀alkyl or C₆ to C₁₀ aryl radical, preferably for hydrogen or astraight-chained C₁ to C₃ alkyl radical and R⁸ is a straight-chained orbranched C₁ to C₁₀ alkylene or C₆ to C₁₄ arylene radical, preferably astraight-chained or branched C₁ to C₅ alkylene radical or phenylene.

[0020] Furthermore, the invention relates to the use of thesehydrolysis-stable acrylic ester phosphonic acids for the preparation ofpolymers, adhesives, dental materials or other materials and substances.The subject-matter of the present invention is also the use of theacrylic ester phosphonic acids as a component of adhesives, cements,composites, shaped bodies or dental materials as well as polymers orcopolymers, which can be obtained by homo- or copolymerization of theacrylic ester phosphonic acids.

[0021] The following preferred definitions, which unless otherwisestated can be chosen independently of each other, exist for theabove-mentioned variables of Formula (I):

[0022] n=1,

[0023] R¹=

[0024] R²=a C₁ to C₆ alkylene radical;

[0025] R³=hydrogen, a C₁ to C₃ alkyl radical; and

[0026] R⁴, R⁵=independently of each other, in each case a C₁ to C₃ alkylradical.

[0027] Preferred compounds are accordingly those in which at least oneof the variables of Formula (I) has the above-described preferreddefinition. Particularly preferred monomers according to the inventionare those in which all the variables have one of the preferred meanings.

[0028] The acrylic ester phosphonic acids of Formula (I) according tothe invention can be prepared by esterification of correspondingOH-group-containing mono-(n=1) or difunctional (n=2) R¹—(OH)_(n)compounds with suitable COOH-group-containing acrylate ether phosphonicacid esters AEPE analogously according to the methods for thepreparation of carboxylic acid esters known from the literature (cf.among others B. Neises, W. Steglich, Angew. Chem. 90 (1978) 556, or AHassner, V. Alexanian, Tetrahedron Lett. 46 (1978) 4475) in the presenceof dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP),hydrolytic splitting-off of the protective groups (SG) by silylationwith trialkylsilanes, e.g. trimethylsilyl chloride/NaI or bromide(TMSBr), and subsequent reaction with alcohols, such as e.g. methanol,or water (S. Freeman, J. Chem. Soc., Perkin Trans. 2 (1991) 263.).

[0029] General:

CONCRETE EXAMPLE

[0030]

[0031] The suitable COOH-group-containing acrylate ether phosphonic acidesters AEPE can be synthesized from the corresponding carboxylic acidesters by partial hydrolysis, e.g. with an equimolar quantity of lye at−5° C. analogously to the literature (cf. N. Moszner, F. Zeuner, U. K.Fischer, V. Rheinberger, Macromol. Chem. Phys. 200 (1999) 1062).

[0032] Preferred examples of the acrylic ester phosphonic acids,according to the invention, of Formula (I) are:

[0033] The acrylic ester phosphonic acids according to the invention arestrongly acid and very easily soluble in water or mixtures of water withpolar solvents, such as acetone, ethanol, acetonitrile ortetrahydrofuran (THF). In these, the acidic phosphonic-acid group isbonded to the acrylate group capable of polymerization via ahydrolysis-stable ether group. In addition, the ester group also has inthe acrylic ester phosphonic acids according to the invention a highhydrolysis stability which, taken together, represents a clearimprovement in comparison with conventional polymerizable acrylicphosphonic acids.

[0034] In connection with the present invention, compounds which arestable in water or in mixtures of water and water-miscible solvents in aconcentration of approx. 20 wt.-% and a pH value of approx. 2.0 at 37°C. for at least 6 weeks, i.e. hydrolyze to less than 1%, are describedas hydrolysis-stable.

[0035] As a result of the presence of polymerizable groups, the acrylicphosphonic acid esters according to the invention are suitable asstarting materials for the preparation of polymers and copolymers. Theycan be homopolymerized with the known methods of radical polymerizationor copolymerized e.g. with suitable comonomers.

[0036] The acrylic ester phosphonic acids according to the invention canbe used in free form or in the form of their salts, i.e. as phosphonatesor phosphonate esters, wherein, in the case of the salts, preferablyalkali metal ions, in particular sodium and lithium ions, as well asorganic ammonium ions serve as counterions, in particular those whichare derived from amine accelerators, such asN,N-dihydroxyethyl-p-toluidine,N,N-bis(2-hydroxy-3-methacryloxypropyl-3,5-xylidine or4-(dimethylamino)-benzoic acid-2-ethyl-hexylester. Amine acceleratorsare used in dentistry as a component for example of photoinitiatorsystems. Generally tert. amines are involved which can act as H-donorsand therefore accelerate radical formation (cf. L. A. Linden,“Photocuring of Polymeric Dental Materials and Plastic Composite Resins”in Radiation Curing in Polymer Science and Technology, Vol. IV, J. P.Fouassier, J. F. Rabek (Ed.), Elsevier Appl. Sci., London, New York1993, 396f.).

[0037] The known radical initiators can be used to carry outpolymerization (cf. Encyclopedia of Polymer Science and Engineering,Vol. 13, Wiley-Interscience Publisher, New York 1988, 754 ff.).

[0038] In order to initiate radical photopolymerization, preferablybenzophenone, benzoin as well as their derivatives or α-diketones ortheir derivatives such as 9,10-phenanthrenequinone,1-phenyl-propane-1,2-dion, diacetyl or 4,4-dichlorobenzyl can be used.Preferably camphorquinone and 2,2-methoxy-2-phenyl-acetophenone andparticularly preferably a-diketones are used in combination with aminesas reducing agents, such as e.g. 4-(dimethylamino)-benzoic-acid ester,N,N-dimethylaminoethyl methacrylate, N,N-dimethyl-sym.-xylidine ortriethanolamine.

[0039] In particular azo compounds, such as azobis(isobutyronitrile)(AIBN) or azobis-(4-cyanovaleric acid) or peroxides, such as dibenzoylperoxide, dilauroyl peroxide, tert.-butyl peroctoate, tert.-butylperbenzoate or di-(tert.-butyl)-peroxide are suitable as thermalinitiators. Benzopinacol and 2,2′-dialkyl benzopinacols are alsosuitable as initiators for hot-curing. Redox initiator combinations,such as e.g. combinations of benzoyl peroxide withN,N-dimethyl-sym.-xylidine or N,N-dimethyl-p-toluidine, are used asinitiators for a polymerization carried out at room temperature. Inaddition, redox systems consisting of peroxides and such reducingagents, such as e.g. ascorbic acid, barbiturates or sulphinic acids, arealso particularly suitable.

[0040] The subject-matter of the invention is also compositions whichcontain one or more acrylic ester phosphonic acids according to Formula(I) and additionally also an initiator for radical polymerization.

[0041] As a result of the hydrolysis stability of the acrylic esterphosphonic acids according to the invention, the compositions arestorage-stable at room temperature even in the presence of water and aresuitable in particular as adhesives or cements above all for dentalapplications.

[0042] Compositions are also preferred which, in addition to acrylicester phosphonic acid and optionally initiators, also contain one ormore radically polymerizable monomers.

[0043] Monofunctional and/or multifunctional radically polymerizablemonomers, in particular difunctional crosslinking monomers, are suitableas comonomers. By monofunctional monomers is meant compounds with oneradically polymerizable group, by multifunctional monomers is meantcompounds with two and more radically polymerizable groups. Above allcrosslinking bi- or multifunctional acrylates or methacrylates, such ase.g. bisphenol-A-di(meth)acrylate, bis-GMA (the addition product ofmethacrylic acid and bisphenol-A-diglycidyl ether), UDMA (the additionproduct of hydroxyethyl methacrylate and 2,2,4-trimethylhexamethylenediisocyanate), di-, tri- or tetraethylene glycol di(meth)acrylate,trimethylolpropane tri(meth)acrylate and pentaerythritetetra(meth)acrylate, are suitable for the preparation of adhesives ordental materials. The compounds butanediol di(meth)acrylate,1,10-decanediol di(meth)acrylate and 1,12-dodecanediol di(meth)acrylate,which can be obtained by esterification of (meth)acrylic acid with thecorresponding diols, are also suitable.

[0044] Particularly preferred radically polymerizable monomers areacrylamides or hydroxyalkyl acrylamides.

[0045] As a result of their hydrolysis stability, amides of generalformula BX_(n) are particularly preferred, in which

[0046] B stands for a hydrocarbon radical with 1 to 50 carbon atoms,substituted n times by the group X′, which can contain one or more ofthe groups O, S, NH, CO—NH, NH—CO, NH—CO—O, O—CO—NH and/or NH—CO—NH,

[0047] X′ stands for the group

[0048] which is bound to the radical B via the nitrogen atom or via C-2,the binding site not connected to B carrying a radical R^(2′).

[0049] R^(1′) is hydrogen, an alkyl group with 1 to 20 carbon atoms or aphenyl radical, wherein two or more radicals X′ can share a radicalR^(1′) and wherein R^(1′) can also be a component of the radical B,

[0050] R^(2′) is hydrogen, an alkyl group with 1 to 20 carbon atoms or aphenyl radical, and

[0051] n′ is a number from 2 to 5.

[0052] Group X′ represents the N-substituted amide groups which arebound to the radical B via amide nitrogen or via the carbon atom C-2.

[0053] Amides of this type, preferred derivatives thereof and theirpreparation are disclosed in DE 101 01 523.

[0054] Also preferred are hydroxyalkyl acrylamides of the formula

[0055] in which

[0056] X″ stands for a C₁ to C₁₂ alkylene radical or C₇ to C₁₅ alkylenephenylene radical, preferably for a C₁ to C₁₀ alkylene radical and quiteparticularly preferably for a C₁ to C₈ alkylene radical,

[0057] —R^(1″) stands for a C₁ to C₁₀ alkyl radical, phenyl or hydrogen,preferably for a C₁ to C₆ alkyl radical or hydrogen, particularlypreferably a C₁ to C₃ alkyl radical or hydrogen,

[0058] m″,n″ independently of each other, are 0, 1 or 2, where m″+n″ isequal to 2, and

[0059] R^(2″) stands for hydrogen, methyl or X′″—OH, if m″ is greaterthan or equal to 1, or for X′″—OH, if m″ is equal to 0, where X′″ hasone of the meanings given for X″ and is preferably a C₁ to C₆ alkylene,particularly preferably a C₁ to C₃ alkylene, and

[0060] where for n″=2 the two radicals R^(1″) and for m″=2 the tworadicals —X″— can be the same or different. The above hydroxyalkylacrylamides contain no aldehyde groups.

[0061] The named alkyl and alkylene radicals are preferably lineargroups. Compounds in which m″ und n″ are each equal to 1 areparticularly preferred. Compounds which have 1, 2 or 3 hydroxyl groupsper molecule are also preferred.

[0062] Hydroxyalkylamides of this type, preferred derivatives thereofand their preparation are described in DE 102 28 540.

[0063] Preferred monofunctional radically polymerizable monomers whichare suitable in particular as diluting monomers are hydrolysis-stablemono(meth)acrylates, such as e.g. mesityl methacrylate, or2-(alkoxymethyl)acrylic acids, such as e.g. 2-(ethoxymethyl)acrylicacid, 2-(hydroxymethyl)acrylic acid, N-mono- or -disubstitutedacrylamides, such as e.g. N-ethylacrylamide, N,N-dimethacrylamide,N-(2-hydroxyethyl)acrylamide or N-(2-hydroxyethyl)-N-methyl-acrylamide,as well as N-monosubstituted methacrylamides, such as e.g.N-ethylmethacrylamide or N-(2-hydroxyethyl)methacrylamide and alsoN-vinylpyrrolidone or allyl ether.

[0064] Preferred multifunctional radically polymerizable monomers whichare suitable in particular as crosslinking monomers arehydrolysis-stable urethanes from 2-(hydroxymethyl)acrylic acid anddiisocyanates, such as e.g. 2,2,4-trimethyl hexamethylene diisocyanateor isophorone diisocyanate, crosslinking pyrrolidones, such as e.g.1,6-bis(3-vinyl-2-pyrrolidonyl)hexane, or commercially availablebisacrylamides such as methylene or ethylene bisacrylamide, orbis(meth)acrylamides, such as e.g.N,N′-diethyl-1,3-bis(acrylamido)-propane,1,3-bis(methacrylamido)-propane, 1,4-bis(acrylamido)-butane or1,4-bis(acryloyl)-piperazine, which can be synthesized by reaction fromthe corresponding diamines with (meth)acrylic acid chloride.

[0065] The compositions can contain one or more of the named comonomers.Compositions which contain at least one multifunctional radicallypolymerizable monomer are preferred.

[0066] Furthermore, the compositions according to the invention forimproving the mechanical properties or for setting the viscosity can befilled with organic or inorganic particles. Preferred inorganicparticulate fillers are amorphous spherical materials based on oxides,such as ZrO₂ and TiO₂ or mixed oxides of SiO₂, ZrO₂ and/or TiO₂,nanoparticulate or microfine fillers, such as pyrogenic silicic acid orprecipitation silicic acid as well as mini fillers, such as quartz,glass ceramic or glass powder with an average particle size of 0.01 to 1μm as well as x-ray opaque fillers, such as ytterbium trifluoride ornanoparticulate tantalum(V) oxide or barium sulphate.

[0067] Furthermore, the compositions according to the invention cancontain radically polymerizable phosphoric-acid derivatives.Hydrolysis-stable phosphoric-acid derivatives, such as(meth)acrylamidoalkyl dihydrogen phosphates, in particular6-(N-methacryloylamino)hexyl- and2-(N-methacryloylamino)ethyl-dihydrogen phosphate, are preferred. Thesecompounds improve the etching effect of the composition and aretherefore suitable in particular for the preparation of self-etchingdental materials, such as adhesives and cements. Here, alkyl stands forC₁ to C₁₂ alkyl, preferably for C₁ to C₆ alkyl.

[0068] In addition, the compositions according to the invention alsocontain preferably a solvent, such as ester, e.g. ethyl acetate,preferably water, ethanol, acetone, methylene chloride, acetonitrile ormixtures thereof. Compositions which contain water or a hydrous solventmixture as solvent are preferred.

[0069] The compositions according to the invention can also containfurther additives, e.g. stabilizers, aromatics, microbiocidal activeingredients, fluoride-ion-releasing additives, optical brighteners,plasticizers and/or UV absorbers.

[0070] Compositions which contain exclusively hydrolysis-stablecomponents corresponding to the above definition, represent a quiteparticularly preferred version of the invention.

[0071] The compositions according to the invention are suitable inparticular for the preparation of dental materials, such as cements, forexample of self-adhesive fixing cements, and in particular of adhesives.Such adhesives are characterized by a very good adhesion to the toothhard substance and are hydrolysis-stable under moist conditions.

[0072] Preferred dental materials contain the following components (a),(b), (c), (d), (e) and/or (f):

[0073] a) 0.5 to 70 wt.-%, preferably 10 to 60 wt.-% and particularlypreferably 15 to 50 wt.-% acrylic ester phosphonic acid according toFormula (I),

[0074] b) 0.01 to 15 wt.-%, particularly preferably 0.1 to 8.0 wt.-%initiator for radical polymerization,

[0075] c) 0 to 80 wt.-%, preferably 0 to 60 wt.-% and particularlypreferably 10 to 50 wt.-% radically polymerizable monomer,

[0076] d) 0 to 95 wt.-%, preferably 0 to 80 wt.-%, particularlypreferably 10 to 70 wt.-% and quite particularly preferably 20 to 60wt.-% solvent,

[0077] e) 0 to 50 wt.-%, preferably 0 to 30 wt.-%, particularlypreferably 0 to 20 wt.-% and quite particularly preferably 10 to 20wt.-% (meth)acrylamidoalkyl dihydrogen phosphate,

[0078] f) 0 to 75 wt.-%, particularly preferably—depending on the use—0to 20 wt.-% (adhesive) or 20 to 75 wt.-% (cement) filler.

[0079] Compositions which contain at least the components (a), (c) and(d) are particularly preferred.

[0080] The invention is explained in detail in the following withreference to examples.

EXAMPLES Example 1 Synthesis of2-[2-dihydroxyphosphoryl)ethoxymethyl]-acrylicAcid-2,4,6-trimethylphenyl Ester (MAPA)

[0081] Stage 1: 2-[2-dimethoxyphosphoryl)-ethoxymethyl]-acrylicAcid-2,4,6-trimethyl-phenyl Ester (MAPAME)

[0082] 24.5 g (128 mmol)N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide-hydrochloride was addedin portions within 3 h under vigorous stirring to a solution of 27.6 g(116 mmol) 2-[4-(dimethoxyphosphoryl)-2-oxabutyl]-acrylic acid, whichwas prepared according to the literature (N. Moszner, F. Zeuner, S.Pfeiffer, I. Schurte, V. Rheinberger, M. Drache, Macromol. Mater. Eng.286 (2001) 225) by partial hydrolysis of2-[4-(dimethoxyphosphoryl)-2-oxabutyl]-acrylic acid ethyl ester, 1.33 g(11 mmol) 4-dimethylaminopyridine and 15.0 g (116 mmol) mesitol in 60 mlTHF. The mixture was left to react further overnight at roomtemperature. The volatile components were then drawn off and theremaining oily residue was taken up in 250 ml methylene chloride. Themixture was extracted with 0.5N hydrochloric acid, washed neutral anddried over anhydrous sodium sulphate. Finally, all the volatilecomponents were separated in fine vacuum and the crude product purifiedby means of column chromatography: silica gel column, mobile solventTHF/toluene 1:1. 11.9 g MAPAME (29% yield) as colourless oil isobtained.

[0083]¹H-NMR (400 MHz, CDCl₃, ppm): 2.10 (s, 6H, o-CH₃), 2.17 (dt, 2H,PCH₂), 2.27 (s, 3H, p-CH₃), 3.75 (d, 6H, ═CH₃), 3.81 (m, 2H, PCH₂CH ₂),4.34s, 2H, OCH₂C═), 6.07 and 6.56 (2s, 1H, ═CH₂) and 6.87 (s, 2H,C_(ar)H)

[0084]¹³C-NMR (CDCl₃, 100 MHz): 16.1 (OC_(ar). C_(ar).CH₃), 20.8(OC_(ar). C_(ar). C_(ar). C_(ar).CH₃), 24.8 (d, PCH₂CH₂, ¹J_(C,P)=140.2Hz), 52.3 (d, OCH₃, ²J_(C,P)=6.5 Hz), 64.7 (PCH₂ CH₂), 69.2 (OCH₂C═),127.4 (C═CH₂), 129.2 (C_(ar).H), 129.7 (OC_(ar).C _(ar).CH₃), 135.4(OC_(ar). C_(ar). C_(ar). C_(ar). CH₃), 136.4 (C=CH₂), 145.7 (OC_(ar).),163.7 (C═O)

[0085]³¹P-NMR (CDCl₃, 162 MHz): δ =+32.5.

[0086] Stage 2: 2-[2-dihydroxyphosphoryl)-ethoxymethyl]-acrylicAcid-2,4,6-trimethyl-phenyl Ester

[0087] 10.56 g (69 mmol) trimethylsilyl bromide was carefully addeddropwise under argon to a mixture of 9.83 g (27.6 mmol) of the compoundMAPAME and 2.7 mg phenothiazine MEHQ and stirred for 3 h at 45° C. Thenthe mixture was evaporated in a rotary evaporator, reacted with 60 mlmethanol, stirred overnight, evaporated in fine vacuum and dried toconstant weight. 8.77 g (97% yield) of a very viscous oil of MAPAremained.

[0088]¹H-NMR (CDCl₃, 400 MHz): δ =2.08 (s, 6H, o-CH₃), 2.18 (dt, 2H,PCH₂), 2.26 (s, 3H, p-CH₃), 3.82 (m, 2H, PCH₂CH ₂), 4.31 (s, 2H,OCH₂C═), 6.06, 6.55 (in each case s, 1H, ═CH₂), 6.86 (s, 2H, C_(ar).H),9.48 (br, 2H, POH)

[0089]¹³C-NMR (CDCl₃, 100 MHz): δ =16.2 (OC_(ar). C_(ar). CH₃), 20.8(OC_(ar). C_(ar). C_(ar). C_(ar). CH₃), 26.8 (d, PCH₂CH₂, ¹J_(C,P)=143.6Hz), 64.6 (PCH₂ CH₂), 69.2 (OCH₂C═), 127.9 (C═CH₂), 129.2 (C_(ar).H),129.7 (OC_(ar). C_(ar). CH₃), 135.4 (OC_(ar). C_(ar). C_(ar). C_(ar).CH₃), 136.1 (C═CH₂), 145.7 (OC_(ar).), 163.8 (C═O)

[0090]³¹P-NMR (CDCl₃, 162 MHz): δ =+33.6.

Example 2 Examination of the Hydrolysis Stability of MAPA

[0091] A 20% solution of MAPA, stabilized with 200 ppm2,6-di-tbutyl-4-methylphenol, was prepared in D₂O/EtOH-d₆ (1:1), storedat 37° C. and ¹H-NMR-spectroscopically examined. After a standing timeof 2 months, no changes in the ¹H-NMR-spectrum were able to be detected.

Example 3 Preparation of Chemically Curing Adhesives Based on MAPA

[0092] In order to examine dentine adhesion to bovine-tooth dentine,adhesives with the following composition were prepared (figures inwt.-%): TABLE 1 Composition and coefficients of adhesion for dentaladhesives based on MAPA Coefficients MAPA Comonomer Water Initiator ofadhesion 16% 17% HMA ¹⁾ 60% 7%  9.1 ± 2.1 MPa 16% 17% MAHP ²⁾ 60% 7%11.0 ± 3.5 MPa 20% 13% HEMAM ³⁾ 60% 7% 11.0 ± 2.0 MPa 16% 17% DEPBAM ⁴⁾60% 7%  8.8 ± 2.4 MPa

[0093] Bovine teeth were embedded into plastic cylinders such that thedentine and the plastic were located at one level. One layer each of theabove adhesives was massaged for 15 s into the dentine surface with asmall brush and lightly blown with an air syringe. A prepolymerizedcylinder, made from dental composite material (Tetric® Ceram, IvoclarVivadent AG), coated with a self-curing cement was applied to theadhesive layer and cured for 10 minutes in the dark. The test pieceswere then stored in water for 24 h at 37° C. and the shearing adhesivestrength was determined according to the ISO Guideline “ISO 1994-ISO TR11405: Dental Materials Guidance on Testing of Adhesion to ToothStructure”. The results are summarized in Table 1. They show that theacrylic ester phosphonic acids according to the invention are not onlyhydrolysis-stable, but also guarantee a high degree of adhesion betweendentine and composite material.

1. Acrylic ester phosphonic acid of general formula (I), stereoisomersthereof and mixtures of these,

in which n is 1 or 2, on the condition that for n=1 R¹ has the meaning

and for n=2 R¹ has the meaning

R² is a C₁ to C₁₂ alkylene radical, C₄-C₈ cycloalkylene radical or C₇ toC₁₅ alkylene phenylene radical; R³ is hydrogen, a C₁ to C₅ alkyl radicalor a C₁ to C₅ O-alkyl radical; and R⁴, R⁵ independently of each other,each stand for a C₁ to C₅ alkyl radical or a C₁ to C₅ O-alkyl radical.2. Acrylic ester phosphonic acid according to claim 1, characterized inthat one or more of the variables of Formula (I), independently of eachother, have the following meaning: n=1, R¹=

R²=a C₁ to C₆ alkylene radical; R³=hydrogen, a C₁ to C₃ alkyl radical;and R⁴, R⁵=independently of each other, a C₁ to C₃ alkyl radical. 3.Acrylic ester phosphonic acid according to claim 1 or 2, characterizedin that the radicals R², R³, R⁴ and/or R⁵ are unsubstituted orsubstituted by one or more substituents selected from the group Cl, Br,CH₃O, OH, COOH, CN, ═O, ═S, ═NR⁶ or —NR⁷—CO—C(═CH₂)CH₂—Y—R⁸—PO(OH)₂,wherein R⁶ and R⁷, independently of each other, each stand for hydrogen,a straight-chained or branched C₁ to C₁₀ alkyl or C₆ to C₁₀ aryl radicaland R⁸ is a straight-chained or branched C₁ to C₁₀ alkylene or C₆ to C₁₄arylene radical.
 4. Composition, characterized in that it contains anacrylic ester phosphonic acid according to one of claims 1 to
 3. 5.Composition according to claim 4, characterized in that it additionallycontains a radically polymerizable monomer.
 6. Composition according toclaim 5, characterized in that it contains an acrylamide and/or ahydroxyalkyl acrylamide as a radically polymerizable monomer. 7.Composition according to claim 5 or 6, characterized in that it containsa monofunctional and/or a multifunctional radically polymerizablemonomer.
 8. Composition according to claim 7, characterized in that itcontains as a monofunctional radically polymerizable monomer one or morehydrolysis-stable mono(meth)acrylates, mesityl methacrylate, one or more2-(alkoxymethyl)acrylic acids, 2-(ethoxymethyl)acrylic acid,2-(hydroxymethyl)acrylic acid, one or more N-mono- or N-disubstitutedacrylamides, N-ethylacrylamide, N,N-dimethacrylamide,N-(2-hydroxyethyl)acrylamide, N-(2-hydroxyethyl)-N-methyl-acrylamide,one or more N-monosubstituted methacrylamides, N-ethylmethacrylamide,N-(2-hydroxyethyl)methacrylamide, N-vinylpyrrolidone, allyl ether or amixture of two or more of these monomers.
 9. Composition according toclaim 7 or 8, characterized in that it contains as a multifunctionalradically polymerizable monomer one or more urethanes from2-(hydroxymethyl)acrylic acid and diisocyanates,2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, oneor more crosslinking pyrrolidones,1,6-bis(3-vinyl-2-pyrrolidonyl)-hexane, one or more bisacrylamides,methylene bisacrylamide, ethylene bisacrylamide, one or morebis(meth)acrylamides, N,N′-diethyl-1,3-bis(acrylamido)-propane,1,3-bis(methacrylamido)-propane, 1,4-bis(acrylamido)-butane,1,4-bis(acryloyl)-piperazine or a mixture of two or more of thesemonomers.
 10. Composition according to one of claims 4 to 9,characterized in that it additionally contains an initiator for radicalpolymerization.
 11. Composition according to one of claims 4 to 10,characterized in that it additionally contains a filler.
 12. Compositionaccording to one of claims 4 to 10, characterized in that itadditionally contains solvent.
 13. Composition according to one ofclaims 4 to 12, characterized in that it additionally contains a(meth)acrylamidoalkyl dihydrogen phosphate.
 14. Composition according toone of claims 4 to 13, characterized in that it contains a) 0.5 to 70wt.-% acrylic ester phosphonic acid according to claim 1 or 2; b) 0.01to 15 wt.-% initiator for radical polymerization; c) 0 to 80 wt.-%radically polymerizable monomer; d) 0 to 95 wt.-% solvent; e) 0 to 50wt.-%, (meth)acrylamidoalkyl dihydrogen phosphate, and/or f) 0 to 75wt.-% filler.
 15. Use of a composition according to one of claims 4 to14 as dental material.
 16. Use according to claim 15 as cement oradhesive.
 17. Use of an acrylic ester phosphonic acid according to oneof claims 1 to 3 for the preparation of a dental material.